Single mode fiber optic data links have been developed as alternatives to multimode fiber data links. In a single mode fiber, a single spatial mode propagates therethrough so that modal noise effects are reduced. Single mode optical systems, however, may be extremely sensitive to alignment errors. Sensitivity to alignment errors may be particularly critical when a data link is used in an extreme environment with exposure to vibrations and shock. A need thus exists to provide single mode fiber optic connections which have reduced sensitivity to shocks and vibrations. Dust and debris may also be problematic in single mode fiber connections known in the prior art.
A single mode fiber optic connection according to the prior art is illustrated in FIGS. 1 and 2. As shown, two single mode optical fibers 11 are inserted into ferrules 13 that are held together with a spring loaded stainless steel jacket 15. The springs keep the ferrules in compression in an attempt to keep the ferrules in contact at all times. A ceramic sleeve 17 surrounds the ferrules to keep the ferrules and the fibers aligned in the transverse direction. This sleeve is thus precisely machined to tolerances within 1 micron on the inner diameter. Accordingly, as light is transmitted from a first one of the fibers across the junction to the second fiber, residual losses may occur.
The ferrules, however, may piston in and out of the sleeve as a result of severe shocks and/or vibrations thereby creating a gap between the two fibers 11. This gap may increase optical losses beyond acceptable levels. Moreover, a single dust particle between the respective core portions of the two optical fibers may block a significant portion of the radiation being transmitted therebetween.
Gradient Index (GRIN) lenses have been used to collimate and focus light in fiber switching and connecting systems. GRIN lenses, however, may be quite large in comparison with the dimensions of optical fibers thus increasing overall package sizes and reducing switching densities. GRIN lenses may also be limited to simple optical focusing and collimation functions while current broadband networks may require complex functions for Wavelength Division Multiplexing (WDM).
Accordingly, there continues to exist a need in the art for improved methods and structures for joining two optical fibers to reduce optical losses for signals transmitted therebetween.